The unicellular eukaryote, Tetrahymena thermophila, has two kinds of nuclei: the diploid micronucleus (MIC), the germline nucleus which can undergo meiosis; the 45C macronucleus (MAC), the somatic nucleus which is replaced each sexual generation from micronuclear products. The long-term goal of the proposed research is to investigate the molecular events underlying the development and differentiation of the MAC, during which, genome alterations occur. We will use specific cloned MIC sequences in hybridization experiments with DNA obtained from MIC or MAC at various stages and states of differentiation to find out: (i) when alterations occur during the life cycle of the MAC; (ii) whether they occur randomly; (iii) how the MIC sequences being altered are distributed on MIC chromosomes; (iv) whether the sequences being altered are transcribed; (v) which processes cause genome alterations; (vi) what sequences are associated with these processes. First, we will focus on special kinds of sequences. Then, we will attempt to isolate a specific gene which codes for a protein. Our methodology includes cell cloning, gene cloning, chromosome mapping, restriction mapping, analysis of genomic DNA blots with specific probes, electron microscopy, DNA sequencing, and other biochemical procedures. These studies should contribute towards understanding how alterations in DNA molecules occur in normal cells of eukaryotic organisms during development and differentiation.